Table 2.
An overview of tissues in which sperm associated antigens (SPAGs) are expressed
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|---|---|---|
| SPAGs | Organs/cells | Cellular status |
|
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| SPAG1 | Lungs, Large intestine, Kidneys, Braini, Testicles, Neck, and midpiece of pachytene primary Spermatocytes (UniProt ID Q07617) | Part of the cytoskeleton microtubules in the Cytoplasm |
| SPAG2/UAP1 | Testicle, Somatic tissuesii, Low expression level in Placenta, Muscle, and Liver (UniProt ID Q16222) | Cytoplasm |
| SPAG3/ HSPA2 | Ubiquitous, Globus pallidusi (UniProt ID P54652; GeneCard ID GC14P064535) | Cytoskeleton and mitotic cell cycle |
| SPAG4 | Testicle, Sperm cells (UniProt ID Q9NPE6) | Cytoplasmic membrane, Cytoplasm, Nucleus membrane |
| SPAG5 | Testis, Placenta, Liver, Pancreas, Thymus, Coloniii (UniProt ID Q96R06) | Cytoskeleton, Cytoplasm |
| SPAG6 | Testisiv (UniProt ID O75602) | Cytoskeleton, Flagellum |
| SPAG7 | Fetal brain (UniProt ID O75391) | Nucleus |
| SPAG8 | Testis germ cellsv (UniProt ID Q99932) | Nucleus, Cytoplasm |
| SPAG9 | Testisi (UniProt ID O60271) | Cytoplasm |
| SPAG10/MFGE8 | Mammary epithelial cell surfacesi, Aortic media (UniProt ID Q08431) | External side of the plasma membrane, Endoplasmic reticulum lumen, can be secreted as extracellular exosome |
| SPAG11B | Caput and proximal corpus of the epididymis, Epididymal epithelium, Sperm head (UniProt ID Q08648; GeneCard ID GC08M007442) | Secretory proteinvi |
| SPAG12/ SNU13/ NHP2L1 | Ubiquitous (UniProt ID P55769) | Dense fibrillar component of the nucleolus |
| SPAG13/ KRAP/SSFA2 | Pancreas, Testis (UniProt ID P28290)i | Plasma membrane, membrane bound arrangement with extracellular regions |
| SPAG15/ SPAM1 | Testisi (UniProt ID P38567) | Human sperm surface, Inner acrosomal membrane |
| SPAG16 | Testis, Brain, Liver, Pancreas, Adrenal gland, Spinal cord, Heart, Thyroid, Trachea, Ovary, Kidneyvii (UniProt ID Q8N0X2) | Axoneme of the tail in sperm cells, Nucleus of post-meiotic germ cells |
| SPAG17 | Testisi (UniProt ID Q6Q759) | Axonemal central apparatus, Cilia-bearing cells consist of Lung, Brain, Uterus, Oviduct, Bronchial, Tracheal epithelial cells |
| SPAG18/ PSMA5 | Ubiquitous (UniProt ID P28066; GeneCard ID GC01M109399) | Cytoplasm, Nucleus |
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i ; High expression level, ii; There are two isoforms of alanine--glyoxylate aminotransferase 1 (AGX1) and AGX2 for SPAG2, which former is numerous in testicle while the latter is more numerous than isoform one in somatic tissues, ⅲ; SPAG5 is highly expressed in testis. By contrast, it is detected at a low level in the placenta, liver, pancreas, thymus, and colon, ⅳ; SPAG6 is highly expressed in the testis; however, it is not detected in the prostate, ovary, spleen, thymus, small intestine, colon, and peripheral blood leukocytes, ⅴ; Although it is widely expressed in testis (germ cells), there is no expression in the liver, kidney, prostate, and small intestine, ⅵ; SPAG11 gene encodes several androgen-dependent and epididymis-specific secretory proteins, and ⅶ; It appears to be 5 isoforms for SPAG16, which isoform1 is detected in testis while isoform four has been detected in also testis and brain. Also, it is stated that isoform 4 has a low expression level in the liver, pancreas, adrenal gland, spinal cord, heart, thyroid, trachea, ovary, and kidney.